sl1200mk2
the stock mount for the 46 works great with my Saito 65 and the 65 has the exact same mounting dimensions as the 91 so I have to believe that it will work the same for you as it did for me.
All you have to do is reverse the carb so the needle is going out the other side of the cowl and then grind off the part of the mount that holds the nose wheel. This should offset the carb enough to the left side of the plane for the carb bolt to miss the mount bolt.
If your still having problems let me know and I'll pull my cowl off and take a picture.